1. Field of the Invention
The present invention relates to a process for the preparation of phenoxyphosphazene compounds, flame-retardant resin compositions and flame-retardant resin molded articles.
2. Description of the Related Art
Phenoxyphosphazene compounds are the oligomers or polymers which are prepared by reacting a dichlorophosphazene compound with an alkali metal salt of a phenol compound. The use of these compounds as additives, modifiers, etc., for synthetic resins has been heretofore studied.
Phenoxyphosphazene compounds can impart high flame retardancy, thermal stability, molding processability and other properties to synthetic resins. However, phenoxyphosphazene compounds have a serious drawback: they discolor synthetic resins when added thereto.
In addition, the addition of a phenoxyphosphazene compound to a synthetic resin may deteriorate the heat resistance, weathering resistance, discoloration resistance, chemical resistance and other properties of the synthetic resin in long-term storage, although such deterioration may not be evident shortly after the addition. Especially, resin compositions prepared by adding a phenoxyphosphazene compound to a polycarbonate resin or a mixed resin of a polycarbonate resin and another resin undergo a decrease in molecular weight of the polycarbonate resins during long-term storage. Inevitably, this results in greatly lowered transparency, change in hue such as whiteness, etc., of the polycarbonate resins.
Phenoxyphosphazene compounds are usually washed with an aqueous solution containing an acid such as hydrochloric acid, sulfuric acid or the like, an aqueous solution containing an alkali such as sodium hydroxide, sodium carbonate or the like or water. However, such washing treatment cannot satisfactorily mitigate the above-mentioned drawbacks of phenoxyphosphazene compounds.
Further, when a molding is produced from the resin composition prepared by adding the phenoxyphosphazene compound washed with the aqueous acid solution or aqueous alkaline solution to a synthetic resin, it corrodes the molding device.